The present invention pertains to integrated circuits and particularly to a method of making integrated circuits having a plurality of metal-oxide-semiconductor field-effect transistors that have varying characteristics on a single semiconductor substrate using ion implantation to vary the characteristics thereof.
A method for adjusting the threshold voltage of a MOSFET using ion implantation is described in U.S. Pat. No. 3,898,105. Both enhancement mode and depletion mode MOSFETs can be made as described therein by selectively masking enhancement mode sites against a dose of ions that causes transistors formed in the unmasked sites to operate in the depletion mode. The present invention employs the techniques as generally described in the cited patent in a new and different manner to create circuits with substantially lower response times than were heretofore possible.
The present invention is particularly applicable to improvements in the implementation of certain prior art inverter circuits. A detailed description of such prior art circuits is given in U.S. Pat. No. 3,775,693.